Hydraulic jet propulsion apparatus

ABSTRACT

Hydraulic jet propulsion apparatus for water borne craft and having a variable area discharge nozzle. The nozzle is reversed under power by having a laterally movable reversing portion which can be easily moved in a transverse direction to thereby vary the reverse thrust with good control. The apparatus also includes an improved bearing for the main drive shaft by means of which shrouds or outer sleeves have been eliminated from the water intake thereby increasing the in-flow with less turbulence.

United States Patent [451 Aug. 1, 1972 Aschauer et a1.

[54] HYDRAULIC JET PROPULSION APPARATUS [72] Inventors: George R. Aschauer; Paul E.

Ritenour, both of Racine, Wis.

[73] Assignee: Twin Disc, Incorporated, Racine,

Wis.

[22] Filed: Oct. 12, 1970 [21] Appl. No.: 79,733

[52] US. Cl. ..60/221, 60/230, 239/265.19,

115/14 [51] Int. Cl ..F02k 1/20 [58] Field of Search ..60/221, 222, 242, 243, 271, 60/230; 239/265.11, 265.19, 265.39; 415/214; 115/14 [56] References Cited UNITED STATES PATENTS 4/1962 Barnes ..239/265.l9 X 5/1964 Thielman ..239/265.19 UK 9/ 1 966 Rosentrater ..239/265.25

3,594,102 7/1971 Oden ..415/214 UX 3,084,509 4/ 1963 Parsons ..60/222 X 3,121,994 2/1964 Aldropp ..60/222 X 3,336,752 8/1967 Smith ..60/221 855,165 5/1907 Cutler ..60/222 3,034,295 5/1962 Hanley ..60/222 3,137,266 6/1964 Perrier ..60/222 X 3,478,712 11/1969 Fox ..60/221 X Primary Examiner-Douglas Hart Attorney-James E. Nilles [5 7] ABSTRACT Hydraulic jet propulsion apparatus for water borne craft and having a variable area discharge nozzle. The nozzle is reversed under power by having a laterally movable reversing portion which can be easily moved in a transverse direction to thereby vary the reverse thrust with good control. The apparatus also includes an improved bearing for the main drive shaft by means of which shrouds or outer sleeves have been eliminated from the water intake thereby increasing the in-flow with less turbulence.

15 Claims, 9 Drawing Figures PATENT E UA 1 SHEEI 2 OF 5 W a 7 Irmzwzy Hli PATENTEDAm; 1 I972 SHEET 4 OF 5 INVENTORJ PAIENTKMJG 1 I972 SHEU 5 OF 5 BACKGROUND OF THE INVENTION The invention pertains to hydraulic jet propulsion systems having a pump stage that receives water from the intake and discharges it under pressure through the discharge noule extending to the rear of the craft. Prior art discharge nozzles have been used which could be varied as to their area to consequently vary the thrust of the unit. An example of such a variable area jet nozzle is shown in the US. Pat. No. 3,251,185, issued May 17, 1966, and which has been assigned to an assignee common with the present invention. These prior art type of propulsion systems have had several shortcomings, among which is the difficulty in adjusting the area of the nozzle due to the lack of pressure balance in the nozzle. That is to say, as the nozzle was being adjusted, the water pressure reacted differently on different parts of the nozzle thereby causing its unbalance and difficulty in its operation. Furthermore, these prior art units had side vector jets for steering and often these side jets were located with respect to the main variable nozzle so that they were not completely efficient in all positions of the main jet nozzle.

Other prior art devices have been provided for reversing the thrust of these jets and while they did work satisfactorily, many of them had numerous parts which were subject to malfunction and misadjustment and were otherwise inefficient in reversing the thrust of the propulsion system with the required accuracy and degree of control.

Still other prior art devices had drive shafts for the pump, which shafts extended through the intake water passage, and these shafts were shrouded or covered with housings or sleeves which functions to disrupt the incoming water and cause turbulence as well as reduce the capacity of the intake passage. Such a prior art device is shown in the US. Pat. No. 3,405,526, which issued Oct. 15, 1968 and which is also assigned to an assignee common with the present invention. Still a further example of prior art devices is shown in the US Pat. No. 3,328,961, which issued July 4, 1967 and is assigned to a common assignee with the present inventron.

SUMMARY OF THE PRESENT INVENTION The present invention provides a jet propulsion apparatus having a variable area nozzle that is completely balanced by the water pressure acting on it regardless of its position. The invention also includes side vector valves which are located ahead of the main nozzle and which efiiciently perform the steering functions regardless of the position of the main nozzle. These side valves are individually controlled, for example by hydraulic motors, said motors being sequentially tied together so that one valve closes while the opposite one is opening and vice versa. Still another aspect of the present invention relates to reversing mechanism for reversing the thrust discharged from the adjustable nozzle. This reversing mechanism consists of two parts which are transversely slideable in opposite directions. These parts, when close together directly behind the nozzle, act to reverse the thrust of the jet, and they can be slid laterally sideways, to any degree, in separate directions so as to vary the amount of rearward thrust. When the parts are entirely separated, one on each side of the jet stream, no reversing action occurs.

Still another aspect of the invention relates to the means for mounting the main drive shaft including a sliding sealing surface between the housing and the drive shaft and which is located outside of the water intake passage. That portion of the drive shaft which extends through the water intake passage requires no sleeve or housing, thereby permitting maximum inflow of water through the intake passage.

These and other objects and advantages of the present invention will appear hereinafter as this disclosure progresses, reference being had to the accompanying drawings.

BRIEF DESCRIPTION OF THE DRAWINGS FIG. 1 is a perspective view of a jet propulsion apparatus made in accordance with the present invention showing only a fragmentary portion of the water craft to which it is attached;

FIG. 2 is a longitudinal cross sectional view through the forward portion, namely the power transmission and the water inlet passage of the apparatus;

FIG. 3 is a fragmentary, enlarged sectional view of the seal assembly of the drive shaft shown in FIG. 2;

FIG. 4 is a longitudinal, cross sectional view through the rearward portion of the apparatus, namely the pump stages, the variable area nozzle and side jet valves, and the reversing mechanism;

FIG. 5 is a fragmentary, rear elevational view, taken generally along the line 5-5 in FIG. 4, and showing the two parts of the reversing mechanism moved to the extreme laterally outward position, certain parts being shown in section;

FIG. 6 is an enlarged detailed view taken along the line 6-6 in FIG. 5, certain parts being shown as broken away or in section for the sake of clarity;

FIG. 7 is a horizontal sectional view taken generally along the line 7-7 in FIG. 4 and showing the side steering valves and the main variable area nozzle;

FIG. 8 is a sectional view of the side jet valves, the view being taken generally along the line 8-8 in FIG. 7 but onan enlarged scale; and

FIG. 9 is a sectional view of the supporting and guiding rollers for the reversing mechanism, the view being taken generally along the line 9-9 in FIG. 5, but on an enlarged scale.

DESCRIPTION OF A PREFERRED EMBODIMENT Referring to the general organization of the propulsion apparatus, the water intake is through the opening 1 (FIG. 2) in the bottom 2 of the craft and the inlet passage 3 extends upwardly and to the rear at a gradually inclined angle. The housing 4 (FIG. 1) for the water inlet passage terminates in a flange 5 which is secured to a flange 6 of the pump housing 7. The pump housing 7 contains the first stage pump 8 (FIG. 4) and the second stage pump 9, both of which pumps are fixed to the drive shaft 10 for rotation therewith at the same speed.

The drive shaft 10 is driven from the power transmission T (FIG. 2) which receives its power from the engine E in the craft. The transmission includes a housing H, and a water tight, sliding seal SS is located between the housing H and the drive shaft 10. A similar seal ss is located between the shaft 10 and the housing 31 (FIG. 4) of the pump section.

These sealing arrangements are shown in greater detail in FIG. 3 and include a stationary carrier 1 1 fixed to the housing H by the bolt means 12. A sealing member 13, preferably made of carbon and ground to a precise flatness is held by the carrier 11 and O-ring seal 14 is provided therebetween. Bearing against the carbon member 13 and forming a sliding seal fit therewith is a nose member 15 preferably formed from tungsten carbide or the like and which is also ground to the desired flatness for sliding and sealing engagement with the member 13. The nose member 15 is cemented'to a rubber boot 16, the boot in turn being urged against the shaft by means of the metal ring 17. The boot 16 and the nose piece are biased against the member 13 for sealing engagement therewith by means of the spring 18 which acts against the axially fixed ring 20and the sleeve 21 fixed to the ring 17. This sealing arrangement provides a water-tight seal between the housing H and the shaft 10, the rotary sliding sealing joint being between the grounded flat members 13 and 15. An 0- ring seal 32 is provided between shaft 10 and housing portion 33.

With this sealing construction, the shaft 10 can extend through the water inlet passage without the necessity of any protecting housings or sleeves. Shaft 10 is of reduced diameter in the passage 3.

The rearward end of the drive shaft is joumalled in anti-friction bearings (FIG. 4) in the housing 31 of enclosed chamber 31a of pump section 7.

The main variable area nozzle N (FIG. 4) is located in a housing 34 which is generally circular when viewed.

in longitudinal vertical cross section. The nozzle N has a wide mouth 35 which generally converges in a rearward direction to terminate in a generally narrower discharge portion 36. The upper surface 37 of the nozzle N is generally curved downwardly in a rearward direction, asv indicated, while a lower surface 38 of the nozzle is also curved upwardly in a rearward direction. The side walls 40 and 41 of the nozzle are flat and generally vertical, thereby providing a generally rectangular cross sectional area to the nozzle when viewed in a transverse and generally vertical plane.

The nozzle is shown in the position for maximum discharge of water, that is in a fully open position.

The nozzle is rotatably mounted about its shaft 42 (FIGS. 1, 4 and 7) said shaft being fixed to a bifurcated arm 43 (FIGS. 1 and 4). The upper end of the arm is swung in forward and reverse directions by the double action hydraulic cylinder means 45 which is under control of the operator. By contracting the cylinder means 45, the nozzle is caused to rotate in a counterclockwise direction as viewed in FIG. 4, thereby causing the rear portion 36 of the nozzle to partially close against the upper portion of the housing 34. Thenozzle can be rotated from the position shown in FIG. 4, in a counter-clockwise direction to a point where it completely closes the valve and no further rearward discharge occurs.

The above-described nozzle is balanced by hydraulic pressure regardless of its position, because the incoming water pressure is always acting against both the surfaces 37 and 38. Furthermore, water pressure is also present in the chambers 48 and 49 between the nozzle and the housing 34, by leaking between the nozzle and the housing, thereby contributing to hydraulic balance of the entire unit. With this arrangement, the nozzle is easily and accurately controlled.

Side steering valves V1 and V2 (FIGS. 1, 4, 7, and 8) are located ahead of the main nozzle N and are consequently subjected to full water pressure at all times. These valves are located in opposite sides of the housing 34 and extend directly laterally therefrom and are of the butterfly type. These butterfly valves are operated sequentially, through the crank arm 50 by means of the double action cylinder means 51 and 52, respectively. The operation is such that as one valve closes, the other opens thereby permitting water to be forced laterally to one side or the other thereby causing steering of the craft.

The jet propulsion apparatus also includes mechanism for reversing the thrust discharged by the nozzle to thereby slow down the craft or cause it to operate in the reverse direction. This reverse mechanism RM includes laterally separable parts 60 and 61 which slide laterally on the upper track 63 and lower track 64, under the influence of double acting hydraulic cylinder means 66 and 67, respectively. These parts 60 and 61 move together either in an inwardly or outwardly direction so as to respectively, either be directly behind the discharge end of the nozzle to receive the full jet stream therefrom for reversing, or in a laterally outward position where no jet stream is engaged by the parts 60 and 61 and as a result the craft moves straight ahead. These parts 60 and 61 can also be moved to an intermediate position behind the jet stream to absorb a portion of the stream to efiect slow-down of the craft.

The parts 60 and 61 are generally U-shaped in character. The open end, of the U facing in a forward direction in respect to the water craft. A plurality of upper rollers 73 are carried by each of the parts for engagement in the upper track 63. A plurality of lower rollers 74 are carried by each of the parts 60 and 61 for engagement in the lower guide and supporting track 64. This mounting means for the parts 60 and 61 provide an accurate and easily controlled movement of the parts through the operation of the double acting hydraulic cylinder means 66 and 67. As shown in FIGS. 6 and 9, these rollers are staggered, that is to say, two of the rollers 73a and 73b are located rearwardly of the third roller 73c and the load is actually carried by these two rollers of each set of three rollers. The third roller 73c acts as a guiding and incidental bearing roller and by so staggering these rollers, good alignment-and assembly is possible.

By means of the present invention, a variable area nozzle is provided which is fully balanced in a horizontal sense regardless of its position. The side vector steering valves are located ahead of the main nozzle and subjected to full thrust pressure at all times for good steering characteristics.

' The reversing mechanism includes two laterally separable parts which are adjustable as to their relative position so as to provide accurate and good reversing and slowing characteristics.

The power shaft through the inlet passages of the propulsion apparatus requires no housing due to the particularly efficient seal between the housing and the forward parts of the shaft, thereby contributing to maximum water intake and little turbulence.

We claim:

1. Jet propulsion apparatus fora water craft including a water intake housing, pump means for receiving water from said housing and discharging it rearwardly, a nozzle located rearwardly of said pump means-for receiving water under pressure therefrom, a nozzle housing for rotatably supporting said nozzle, said nozzle comprising, an uppersurface and a lower surface which converge together in a rearwardly directly to ter minate in a rear portion, said noule also comprising side walls interconnected between said upper and lower portions, said nozzle being rotatable about a generally horizontal and transverse axis within said housing, said rear portion of said nozzle havinga portion of its area blocked by said housing when the nozzle rotates to thereby vary the effective discharge area of the nozzle, said water pressure being discharged by said pump means acting on both upper and lower surfaces of said nozzle regardless of the position thereof so as to maintain hydraulic balance of the nozzle.

2. The apparatus set forth in claim 1 further characterized in that said upper surface of said nozzle is curved downwardly in a rearward direction, said lower surface curves upwardly in a rearward direction, both of said surfaces defining a relatively high mouth of said nozzle as compared to said rear portion of said nozzle, said surfaces together with said nozzle side walls defining a generally rectangular cross section in a vertical transverse plane.

3. The apparatus set forth in claim 1, including side vector steering valves, one on either side of said nozzle housing and extending outwardly therefrom, said steering valves being located ahead of said nozzle and subjected to full water pressure at all times.

4. The apparatus set forth in claim 3 further characterized in that said steering valves are of the butterfly type, and power means are connected to said valves for operation thereof.

5. In a jet propulsion apparatus of the type having an intake, pump means, and a discharge nozzle wherein water under pressure is discharged rearwardly of said nozzle to drive a water craft, reversing mechanism connected at the discharge end of said nozzle and comprising, a pair of generally U-shaped channel parts having their inlet end adjacent the discharge end of said nozzle, and means for slideably mounting said parts in lateral and opposite directions on said water craft whereby said parts can be moved laterally together to a position directly behind said nozzle for receiving the full jet stream therefrom, and a position laterally separated apart and away from said nozzle whereby said jet stream can pass directly therebetween.

6. The apparatus set forth in claim 5 further characterized in that said mounting means includes an upper and a lower track means secured to said water craft, roller means mounted on said parts for engagement within said tracks, and power means to selectively move said parts in lateral directions along said track means.

7. Jet propulsion apparatus for a water craft including a water intake housing, pump means for receiving water from said housing and discharging it rearwardly, a nozzle located rearwardly of said pump means for receiving water under pressure therefrom, a nozzle housing for rotatably supporting said nozzle, said nozzle comprising, an upper surface and a lower surface which converge together in a rearwardly direction to terminate in a rear portion, said nozzle also comprising side walls interconnected between said upper and lower portions, said nozzle being rotatable about a generally horizontal axis within said housing, said rear portion of said nozzle cooperating with said housing when the nozzle rotates to thereby vary the effective discharge area of the nozzle, said water pressure being dischargedby said pump means acting on both upper and lower surfaces of said nozzle regardless of the position thereof so as to maintain hydraulic balance of the nozzle, and reversing mechanism connected at the discharge end of said nozzle and comprising, a pair of generally U-shaped channel parts having their inlet end adjacent the discharge end of said nozzle, and means for slideably mounting said parts in lateral and opposite directions on said water craft whereby said parts can be moved laterally together to a position directly behind said nozzle for receiving the full jet stream therefrom, and a position laterally separated apart and away from said nozzle whereby said jet stream can pass directly therebetween.

8. The apparatus set forth in claim 7 further characterized in that said mounting means includes an upper and a lower track means secured to said water craft, roller means mounted on said parts for engagement within said tracks, and power means to selectively move said parts in lateral directions along said track means. 1

9. The apparatus set forth in claim 7, including side vector steering valves, one on either side of said nozzle housing and extending outwardly therefrom, said steering valves being located ahead of said nozzle and subjected to full water pressure at all times.

10. The apparatus set forth in claim 9 further charac terized in that said steering valves are of the butterfly type, and power means are connected to said valves for operation thereof.

1 1. Jet propulsion apparatus for a water craft including an inlet housing defining a water inlet passage, said housing having an inlet at the bottom of said water craft, said passage extending upwardly and rearwardly from said inlet, pump means rotatably mounted rearwardly of and in communication with said passage, a power shaft extending through said housing and rearwardly through said passage, said shaft being journalled in said housing, a sliding seal means between said housing and said shaft and located forwardly of said passage to form a water tight seal between said shaft and said housing whereby said shaft can extend unobstructively through said passage, a nozzle located rearwardly of said pump means for receiving water under pressure therefrom, a nozzle housing secured to said inlet housing and for rotatably supporting said nozzle, said nozzle comprising, an upper surface and a lower surface which converge together in a rearwardly directly to terminate in a rear portion, said nozzle also comprising side walls interconnected between said upper and lower portions, said nozzle being rotatable about a generally horizontal and transverse axis within said housing, said rear portion of said nozzle having a portion of its area blocked by said housing when the nozzle rotates to thereby vary the effective discharge area of the nozzle, said water pressure being discharged by said pump means acting on both upper and lower'surfaces of said nozzle regardless of the position thereof so as to maintain hydraulic balance of the nozzle.

12. The apparatus set forth in claim 11 including, a

' said nozzle for receiving the full jet stream therefrom,

and a position laterally separated apart and away from said nozzle whereby said jet stream can pass directly therebetween.

13. The apparatus set forth in claim 12 further characterized in that said mounting means includes an upper and a lower track means secured to said water 8 craft, roller means mounted on said parts for engagement within said tracks, and power means to selectively move said parts in lateral directions along said track means. 7

14. The apparatus set forth in claim 11, including side vector steering valves, one on either side of said nozzle housing and extending outwardly therefrom, said steering valves being located ahead of said nozzle and subjected to full water pressure at all times.

15. The apparatus set forth in claim 14 further characterized in that said steering valves are of the butterfly type, and power means areconnected to said valves for operation thereof.

a: a r r m 

1. Jet propulsion apparatus for a water craft including a water intake housing, pump means for receiving water from said housing and discharging it rearwardly, a nozzle located rearwardly of said pump means for receiving water under pressure therefrom, a nozzle housing for rotatably supporting said nozzle, said nozzle comprising, an upper surface and a lower surface which converge together in a rearwardly directly to terminate in a rear portion, said nozzle also comprising side walls interconnected between said upper and lower portions, said nozzle being rotatable about a generally horizontal and transverse axis within said housing, said rear portion of said nozzle having a portion of its area blocked by said housing when the nozzle rotates to thereby vary the effective discharge area of the nozzle, said water pressure being discharged by said pump means acting on both upper and lower surfaces of said nozzle regardless of the position thereof so as to maintain hydraulic balance of the nozzle.
 2. The apparatus set forth in claim 1 further characterized in that said upper surface of said nozzle is curved downwardly in a rearward direction, said lower surface curves upwardly in a rearward direction, both of said surfaces defining a relatively high mouth of said nozzle as compared to said reaR portion of said nozzle, said surfaces together with said nozzle side walls defining a generally rectangular cross section in a vertical transverse plane.
 3. The apparatus set forth in claim 1, including side vector steering valves, one on either side of said nozzle housing and extending outwardly therefrom, said steering valves being located ahead of said nozzle and subjected to full water pressure at all times.
 4. The apparatus set forth in claim 3 further characterized in that said steering valves are of the butterfly type, and power means are connected to said valves for operation thereof.
 5. In a jet propulsion apparatus of the type having an intake, pump means, and a discharge nozzle wherein water under pressure is discharged rearwardly of said nozzle to drive a water craft, reversing mechanism connected at the discharge end of said nozzle and comprising, a pair of generally U-shaped channel parts having their inlet end adjacent the discharge end of said nozzle, and means for slideably mounting said parts in lateral and opposite directions on said water craft whereby said parts can be moved laterally together to a position directly behind said nozzle for receiving the full jet stream therefrom, and a position laterally separated apart and away from said nozzle whereby said jet stream can pass directly therebetween.
 6. The apparatus set forth in claim 5 further characterized in that said mounting means includes an upper and a lower track means secured to said water craft, roller means mounted on said parts for engagement within said tracks, and power means to selectively move said parts in lateral directions along said track means.
 7. Jet propulsion apparatus for a water craft including a water intake housing, pump means for receiving water from said housing and discharging it rearwardly, a nozzle located rearwardly of said pump means for receiving water under pressure therefrom, a nozzle housing for rotatably supporting said nozzle, said nozzle comprising, an upper surface and a lower surface which converge together in a rearwardly direction to terminate in a rear portion, said nozzle also comprising side walls interconnected between said upper and lower portions, said nozzle being rotatable about a generally horizontal axis within said housing, said rear portion of said nozzle cooperating with said housing when the nozzle rotates to thereby vary the effective discharge area of the nozzle, said water pressure being discharged by said pump means acting on both upper and lower surfaces of said nozzle regardless of the position thereof so as to maintain hydraulic balance of the nozzle, and reversing mechanism connected at the discharge end of said nozzle and comprising, a pair of generally U-shaped channel parts having their inlet end adjacent the discharge end of said nozzle, and means for slideably mounting said parts in lateral and opposite directions on said water craft whereby said parts can be moved laterally together to a position directly behind said nozzle for receiving the full jet stream therefrom, and a position laterally separated apart and away from said nozzle whereby said jet stream can pass directly therebetween.
 8. The apparatus set forth in claim 7 further characterized in that said mounting means includes an upper and a lower track means secured to said water craft, roller means mounted on said parts for engagement within said tracks, and power means to selectively move said parts in lateral directions along said track means.
 9. The apparatus set forth in claim 7, including side vector steering valves, one on either side of said nozzle housing and extending outwardly therefrom, said steering valves being located ahead of said nozzle and subjected to full water pressure at all times.
 10. The apparatus set forth in claim 9 further characterized in that said steering valves are of the butterfly type, and power means are connected to said valves for operation thereof.
 11. Jet propulsion apparatus for a water crAft including an inlet housing defining a water inlet passage, said housing having an inlet at the bottom of said water craft, said passage extending upwardly and rearwardly from said inlet, pump means rotatably mounted rearwardly of and in communication with said passage, a power shaft extending through said housing and rearwardly through said passage, said shaft being journalled in said housing, a sliding seal means between said housing and said shaft and located forwardly of said passage to form a water tight seal between said shaft and said housing whereby said shaft can extend unobstructively through said passage, a nozzle located rearwardly of said pump means for receiving water under pressure therefrom, a nozzle housing secured to said inlet housing and for rotatably supporting said nozzle, said nozzle comprising, an upper surface and a lower surface which converge together in a rearwardly directly to terminate in a rear portion, said nozzle also comprising side walls interconnected between said upper and lower portions, said nozzle being rotatable about a generally horizontal and transverse axis within said housing, said rear portion of said nozzle having a portion of its area blocked by said housing when the nozzle rotates to thereby vary the effective discharge area of the nozzle, said water pressure being discharged by said pump means acting on both upper and lower surfaces of said nozzle regardless of the position thereof so as to maintain hydraulic balance of the nozzle.
 12. The apparatus set forth in claim 11 including, a reversing mechanism connected at the discharge end of said nozzle and comprising, a pair of generally U-shaped channel parts having their inlet end adjacent the discharge end of said nozzle, and means for slideably mounting said parts in lateral and opposite directions on said water craft whereby said parts can be moved laterally together to a position directly behind said nozzle for receiving the full jet stream therefrom, and a position laterally separated apart and away from said nozzle whereby said jet stream can pass directly therebetween.
 13. The apparatus set forth in claim 12 further characterized in that said mounting means includes an upper and a lower track means secured to said water craft, roller means mounted on said parts for engagement within said tracks, and power means to selectively move said parts in lateral directions along said track means.
 14. The apparatus set forth in claim 11, including side vector steering valves, one on either side of said nozzle housing and extending outwardly therefrom, said steering valves being located ahead of said nozzle and subjected to full water pressure at all times.
 15. The apparatus set forth in claim 14 further characterized in that said steering valves are of the butterfly type, and power means are connected to said valves for operation thereof. 